
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21649.39    170.8367    22457.72    21314.53    21984.25
experime |  17,281    21998.85    175.3793    23054.88    21655.09    22342.61
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -349.4639    244.8328               -829.3442    130.4163
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    diff = mean(control) - mean(experime)                         t =  -1.4274
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0767         Pr(|T| > |t|) = 0.1535          Pr(T > t) = 0.9233
